The Research Of Multi-user Detection Technology In WOCDMA Communication System

Wireless optical code division multiple access(WOCDMA)is a communication mode which introduces the code-division multiple access(CDMA)technology into wireless optical communication system.Besides providing asynchronous communications access,WOCDMA system has many advantages,such as:①multi-users are permitted to access to the same channel stochastically;②It can be constructed for a real sheer all optical communication networks;③high security against interception;④capability in forming variable bit rate networks and mufti-rate networks;⑤high capacity against interception,suppression of narrow band disturbances。It implies a great challenge for the development of future communication networks,especially all optical networks.There are three problems in WOCDMA technology.One problem is the code capacity is small.The second problem is which scheme selected from among the channel codes.The third problem is about mufti-user detection.This paper presented the study of four different common address codes,such as prime code,extend prime code,modify prime code,optimal optical orthogonal code,the characteristic of each code be emulated and get the self-correlation and the interpenetration.The constructions of the prime code,the optimal optical orthogonal code and the incomplete optimized optical orthogonal code have been presented.All kinds of characteristics of these codes have been emulated through MATLAB.With the supporting of the technology of frequency hopping prime code and frequency optical orthogonal code,we get the MPC/OOC code,and study the construction and the characteristic of this code.The reasons of the multi-address disturbance were analyzed.Best detection,traditional detcction and decorrelation detection have been studied.The Gaussi signal model was constructed according to the indoor wireless optical signal channel.To study the wireless optical signal channel by using decorrelation detection and different spread spectrum sequence. Good effects have been show by emulating through MATLAB.Three different Media Access Control(MAC)protocol have been discussed,such as pure ALOHA,S-ALOHA and S-ALOHA-CDMA.Analyzing the network throughput of the WOCDMA access network in different protocol has also analyzed.Finally,the curve has been got through MATLAB and the characteristic of these throughputs compared with each other.